This had only started about today. I was creating a family group, I saved it, & when I went to one of my parks, they didn't appear. I then checked, & the peeps were gone from the group. Now, every time I try to save that family group, the peeps will disappear. I've tried to copy & paste another group & change their name & details, but nothing will work.

Did the peeps folder get write protected? If game is installed in any "Program Files" folder, make sure permissions are set. You could also try the "PeepFactory" (http://www.playtool.com/pages/peepfactor...ctory.html) and see if it helps (it certainly does if you want to specify and generate hundreds or thousands of peeps).